The present invention relates to a novel chemical-sensitization photoresist composition or, more particularly, to a chemical-sensitization photoresist composition used in the photolithographic patterning process for the manufacture of various kinds of electronic devices capable of giving a patterned resist layer having excellent cross-sectional profile and high fidelity as well as high heat resistance of the patterned resist layer with high photosensitivity and exposure dose latitude. The invention also relates to a novel oxime sulfonate compound useful as an acid-generating agent in the chemical-sensitization photoresist composition.
It is a trend in recent years in the photolithographic patterning works for the manufacture of various kinds of electronic devices such as semiconductor devices and liquid crystal display panels that the patterning work is performed by using a chemical-sensitization photoresist composition which contains a relatively small amount of a compound capable of releasing an acid by irradiation with actinic rays and a resinous ingredient susceptible to the changes of solubility behavior in a developer solution induced by the acid. Chemical-sensitization photoresist compositions in general are characterized by high sensitivity to actinic rays and excellent pattern resolution.
Chemical-sensitization photoresist compositions are classified into positive-working compositions and negative-working compositions depending on the type of the solubility change of the resinous ingredient to an aqueous alkaline developer solution by the radiation-generated acid. Namely, the alkali-solubility of the resist layer of a positive-working photoresist composition is increased while the alkali-solubility is decreased in the negative-working photoresist composition by exposure to actinic rays.
The film-forming resinous ingredient in a positive-working photoresist composition is typically an alkali-soluble polyhydroxystyrene resin, of which at least a part of the hydroxy groups are substituted by acid-dissociable substituent groups such as tert-butoxycarbonyl groups, tetrahydropyranyl groups and the like, so as to decrease the solubility of the resin in an alkaline developer solution. In the negative-working photoresist composition, on the other hand, the film-forming resinous ingredient is a combination of an acid-induced crosslinking agent such as melamine resins and urea resins with a polyhydroxystyrene resin, optionally substituted by the above-mentioned acid-dissociable solubility-reducing substituent groups for a part of the hydroxy groups.
The other essential ingredient in the chemical-sensitization photoresist compositions is a compound capable of releasing an acid by irradiation with actinic rays, of which various classes of compounds have been heretofore proposed and actually tested. A class of the most promising acid-generating agents includes oxime sulfonate compounds, in particular, having a cyano group in the molecule. Several compositions containing an oxime sulfonate compound and methods using the same are proposed. For example, European Patent Application 44115 A1 discloses a heat-curable coating solution containing an acid-curable amino resin and an oxime sulfonate compound. Japanese Patent Kokai 60-65072 discloses a method in which a bake-finishing composition containing a heat-curable resin and an oxime sulfonate compound is cured by irradiation with short-wavelength light. Japanese Patent Kokai 61-251652 discloses oxime sulfonate compounds having a substituent group such as ethylenically unsaturated polymerizable groups, epoxy group, hydroxy group and the like, and polymers thereof. Japanese Patent Kokai 1-124848 teaches an image-forming method by the use of a photosensitive composition containing a film-forming organic substance, an oxime sulfonate compound and a photosensitive compound having an aromatic group. Japanese Patent Kokai 2-154266 discloses a photoresist composition containing an alkali-soluble resin, oxime sulfonate compound and sensitivity enhancing crosslinking agent. Japanese Patent Kokai 2-161444 teaches a negative-patterning method by the use of an oxime sulfonate compound. Further, Japanese Patent Kokai 6-67433 discloses a photoresist composition for i-line exposure containing an oxime sulfonate compound.
The oxime sulfonate compounds having a cyano group in the molecule disclosed in the above-mentioned patent documents include:
.alpha.-(p-toluenesulfonyloxyimino)phenyl acetonitrile; PA0 .alpha.-(4-chlorobenzenesulfonyloxyimino)phenyl acetonitrile; PA0 .alpha.-(4-nitrobenzenesulfonyloxyimino)phenyl acetonitrile; PA0 .alpha.-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)phenyl acetonitrile; PA0 .alpha.-(benzenesulfonyloxyimino)-4-chlorophenyl acetonitrile; PA0 .alpha.-(benzenesulfonyloxyimino)-2,4-dichlorophenyl acetonitrile; PA0 .alpha.-(benzenesulfonyloxyimino)-2,6-dichlorophenyl acetonitrile; PA0 .alpha.-(benzenesulfonyloxyimino)-4-methoxyphenyl acetonitrile; PA0 .alpha.-(2-chlorobenzenesulfonyloxy imino)-4-methoxyphenyl acetonitrile; PA0 .alpha.-(benzenesulfonyloxyimino)-2-thienyl acetonitrile; PA0 .alpha.-(4-dodecylbenzenesulfonyloxyimino)phenyl acetonitrile; PA0 .alpha.-(p-toluenesulfonyloxyimino)-4-methoxyphenyl acetonitrile; PA0 .alpha.-(4-dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl acetonitrile; PA0 .alpha.-(p-toluenesulfonyloxyimino)-3-thienyl acetonitrile; and the like.
The molecules of these sulfonate compounds are susceptible to scission of the sulfonate ester linkage by irradiation with actinic rays to generate a corresponding sulfonic acid so that they are useful as an acid-generating agent in the chemical-sensitization photoresist compositions.
It should be mentioned that, while a sulfonic acid is generated from the oxime sulfonate compound by exposure to light, the number of the sulfonic acid molecules released from a molecule of the above-named oxime sulfonate compounds is necessarily limited to one, so that the amount of the acid is also limited. When such an oxime sulfonate compound is used as an acid-generating agent in a negative-working photoresist composition, accordingly, no satisfactory patterned resist layer can be obtained because the width of a line-patterned resist layer cannot be broad enough at the top and the dimensional fidelity and heat resistance of the patterned resist layer cannot be as high as desired along with a relatively low exposure dose latitude.